U.S. Pat. No. 5,000,129 to Fukada et al, issued Mar. 19, 1991, for "Intake System For Internal Combustion Engine" discloses an air intake system for a V-block engine having a central surge tank disposed above the space between the left and right cylinder banks of the engine. This surge tank is operatively integrated with left and right side surge tanks extending above respective banks of cylinders. A communicating passage disposed between discrete side intake passages connects the central surge tank with the left and right surge tanks so that all of the tanks combine to serve as a single surge tank having a large volume for the suppression of intake air interference.
U.S. Pat. No. 5,133,308, issued Jul. 28, 1992, to Hitomi et al for "Intake System For Engine" discloses an intake system for a V-block internal combustion engine having a centralized junction chamber and a plurality of discrete intake passages connecting the junction chamber with respective cylinders of the engine. Rotary valves in the intake passages are operated by actuators responding to a controller that receives engine speed signals to close and open the valves for improving engine torque.
In contrast to the relatively complex structures and processes for regulating air flow found in the above citations and many prior constructions, the present invention provides a straight forward three plenum active intake manifold for an internal combustion engine operative in several alternate modes to produce an improved engine torque curve over the entire range of engine speeds while reducing induction noise and variances in pitch.